The plugin send the doi code to [Crossref Metadata Search](https://search.crossref.org/), get the information and publish a full citation in apa standard with the shortcode [cpdoiresolve ...].
***Citations tools*** uses the [CrossRef Metadata API](http://search.crossref.org/help/api) to retrieve complete publication information using the doi code as a search query. CrossRef is a part of the [doi system](https://dx.doi.org/).
1. Extract the citations-tools.zip file and upload its contents to the /wp-content/plugins/ directory. Alternately, you can install directly from the Plugin directory within your WordPress Install.
2. Activate the plugin through the "Plugins" menu in WordPress.